1. Field of the Invention
The invention related to semiconductor packages and more particularly to a multilayer polymer metal package which has a polyimide insulation layer and vertical interconnection studs which are made of copper.
2. Description of Prior Art
In a Patent Provisional Publication No. 61-248429, there is provided a superstructure comprising multi-levels or planes separated by a plurality of polyimide insulation layers in which vertical interconnections between different levels and a multilayer ceramic substrate are made by a plurality of electrically conductive studs.
On the multilayer ceramic substrate, a coating of a polyimide layer is formed to provide a first metallized conductive pattern thereon. On the polyimide layer, a plurality of copper studs is provided by means of electroplating for an interconnection with the first metallization pattern. A polyamide slurry, which is an intermediate derivative of polyimide polymer, is coated on an entire surface of the ceramic substrate in a manner to cover each top surface of the copper studs. The polyamide slurry is heated and cured to form a coating of a polyimide layer.
After polishing the coating surface of the polyimide layer, an etching operation exposes each top surface of the copper studs. On the polished surface of the polyimide layer, a second metallized conductive pattern is coated by means of sputtering. Thereafter the process is repeatable so as to provide any number of desired levels of metallization.
The polished surface of the polyimide layer, however, is very susceptible to injury so as to render the sputtered pattern difficult to tightly adhere to the surface of the polyimide layer.
At the process of coating the intermediate derivative of polyimide polymer, the derivative (polyamide) chemically react with the top surface of the copper studs to form a chelate compound. The chelate compound has relatively great resistance so that an increased impedance is presented in electrical paths interconnected through the copper studs.
Therefore, it is an object of the invention to provide a method which is capable of sputtering metallized conductive pattern tightly on the surface of the polyimide layer.
It is another object of the invention to provide a method which is capable of preventing a chelate compound from being produced on each top surface of copper studs.